Browsing College of Engineering and Mines (CEM) by Author "Xie, Ning"
Development of durable “green” concrete exposed to deicing chemicals via synergistic use of locally available recycled materials and multi-scale modifiersXie, Ning; Cui, Na (Center for Environmentally Sustainable Transportation in Cold Climates, 2018-02)From the economic and social perspectives, the use of waste materials would not be attractive until their costs and quality can satisfy the construction requirements. In this study, a pure fly ash paste (PFAP) was developed in place of ordinary Portland cement paste (OPCP). This PFAP was prepared at room temperature and without direct alkali activation. The samples were prepared using only the as-received class C coal fly ash, water, and a very small amount of borax (Na2B4O7). On average, the PFAP featured 28-d compressive strength of about 36 MPa, and micro-nano hardness and elastic modulus 29% and 5%, higher than the OPCP, respectively. These mechanical and other properties of the PFAP make it a viable “green” construction binder suitable for a host of structural and non-structural applications. Advanced characterization of the raw material and PFAP pastes was employed to elucidate the hydration mechanisms of this “green” binder. The obtained knowledge sheds light on the role of class C CFA in the hydration process and may benefit the expanded use of various CFAs in cementitious materials.
A Framework for Life Cycle Sustainability Assessment of Road Salt Used in Winter Maintenance OperationsCui, Na; Xie, Ning; Shi, Xianming (Center for Environmentally Sustainable Transportation in Cold Climates, 2016-12)It is important to assess from a holistic perspective the sustainability of road salt widely used in winter road maintenance (WRM) operations. The importance becomes increasingly apparent in light of competing priorities faced by roadway agencies, the need for collaborative decision-making, and growing concerns over the risks that road salt poses for motor vehicles, transportation infrastructure, and the natural environment. This project introduces the concept of Life Cycle Sustainability Assessment (LCSA), which combines Life Cycle Costing, Environmental Life Cycle Assessment, and Social Life Cycle Assessment. The combination captures the features of three pillars in sustainability: economic development, environmental preservation, and social progress. With this framework, it is possible to enable more informed and balanced decisions by considering the entire life cycle of road salt and accounting for the indirect impacts of applying road salt for snow and ice control. This project proposes a LCSA framework of road salt, which examines the three branches of LCSA, their relationships in the integrated framework, and the complexities and caveats in the LCSA. While this framework is a first step in the right direction, we envision that it will be improved and enriched by continued research and may serve as a template for the LCSA of other WRM products, technologies, and practices.